The objective of the proposed research is to study the effects of prenatal and postnatal ethanol exposure on T-lymphocyte development and function in mice. Children who have been prenatally exposed to ethanol have an increased risk of infection, and since T-lymphocytes play a major role in the normal functioning of an immune response, changes in one or more T- lymphocyte subsets could impact on this increased incidence. Animal and human studies of prenatally-exposed offspring have indicated an overall decrease in T-lymphocyte number and responsiveness. For these reasons, we propose to perform a comprehensive analysis of T-lymphocyte subsets. in mice after chronic and acute ethanol exposures to mimic both chronic and binge drinking habits of humans. Specific aims are (1) to study the temporal expression pattern of T- lymphocytes in the developing thymus; (2) to quantitatively analyze peripheral T-lymphocyte subsets, both in the spleen and intestine; and (3) to perform repertoire analysis on a selected portion of peripheral subsets.